1. Field of the Invention
The present invention relates to a stage device, a method for controlling a stage device, an exposure apparatus using the same, and a device manufacturing method.
2. Description of the Related Art
An exposure apparatus is an apparatus that transfers a pattern of an original (reticle) onto a photosensitive substrate (e.g., wafer, glass plate, and the like, where the surface thereof is coated with a resist layer) via a projection optical system in a lithography process in a manufacturing process of a semiconductor element, a liquid crystal display element, and the like. For example, by mounting a wafer on a positioning stage device with the wafer being adhered using suction by a chuck and giving the positioning stage device a scanning movement, the exposure apparatus appropriately changes the position of a wafer to be exposed and repeats projection exposure. Likewise, the positioning stage device is also used when a reticle is mounted for scanning movement.
In recent years, a positioning stage device requires highly accurate positioning and high speed movement. In order to meet such requirements, Japanese Patent Laid-Open No. 2006-136154 discloses a positioning apparatus that employs a linear motor for producing a force between a coil and a permanent magnet. The linear motor controls the current flowing through the coil, where a command current value for a current driver is calculated based on an electrical angle depending on the relative position between the coil and the magnet (i.e., a so-called “commutation processing”), and controls current flowing through the coil. For example, when the positioning apparatus is driven in the horizontal direction by a two-phase linear motor having a phase A and a phase B, a command current value, which is proportional to cos θ in phase A and −sin θ in phase B, is provided to the current driver using the electrical angle θ set by the relative position between the coil and the magnet. When the positioning apparatus is driven in the vertical direction by the linear motor, a command current value, which is proportional to sin θ in phase A and cos θ in phase B, is provided to the current driver.
Here, the aforementioned current driver detects the current flowing through the coil to perform feedback control. However, although it is an ideal that a transfer function from the command current value subjected to commutation processing to the current flowing through the coil is constant regardless of frequency, in practice, the transfer function has frequency characteristics caused by the inductance of the coil, the influence of filter provided in the current driver circuit, and the like. Due to the frequency characteristics, the higher-frequency command current value subjected to commutation processing leads to more delay of the current flowing through the coil. Hence, in the conventional linear motor, a force acting in a direction different from the direction to be driven occurs due to the error current caused by the delay of the current flowing through the coil. Since such force may cause degradation of control characteristics for the linear motor, it is desirable that such a force be excluded as much as possible in order to provide a highly-accurate positioning.